Ak. Theophilou et P. Papaconstantinou, Some properties of the KS potential, concerning degenerate and nearly degenerate states, J MOL ST-TH, 501, 2000, pp. 85-89
We show that the KS potential of a degenerate state depends only on its sym
metric part. The nonsymmetric part has to be abandoned both from the Hartre
e as well as from the exchange and correlation potential. The same picture
prevails when a perturbation breaks the symmetry, i.e. the perturbation KS
potential must have the same transformation properties as the external pote
ntial and must tend to zero when the external perturbation tends to zero. (
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